A. Technical Field
The present invention relates generally to Internet of Things (IOT), and more specifically to near field communication (NFC) and Radio Frequency Integrated Circuit (RFIC) communication.
B. Background of the Invention
The Internet of Things (IOT) is the network of physical objects or “things” embedded with electronics, software, sensors, and connectivity to enable objects to exchange data with the production, operator and/or other connected devices. IOT allows objects to be sensed and controlled remotely across existing network infrastructure, creating opportunities for more direct integration between the physical world and computer-based systems, and resulting in improved efficiency, accuracy and economic benefit.
In IOT applications, power amplifiers are widely used in transmitter (TX) circuit to generate the signal pulse from Card (Emulated) to increase the carrier amplitude to enhance the amplitude modulation received by reader receiver (RX), when TX delivers 1/0 signal.
In PICC and Card Emulation circuit, a Passive Load Modulation (PLM) scheme or an Active Load Modulation (ALM) scheme may be used for transmission. In PLM scheme, the coupled impedance loading the output stage of a reader or a proximity coupling devices (PCD) is variable to implement Amplitude Modulation (AM) to Reader. In ALM scheme, signal is transmitted (and synchronized with the carrier in the field) from tag/PICC device to mimic the behavior of passive load modulation (constructive/destructive interference to the reader) to extend the communication distance.
PLM has the advantage of protecting circuit from high power carrier input from a Reader or PCD by leaking out the most power with its regulator and limiter circuit when PICC is close to PCD (strong field). However, PLM becomes insufficient to deliver the signal when the communication distance is long. ALM can fulfill TX signal delivery at long distance by transmitting modulated signal to interfere PCD's carrier in the air (weak field). However, at short distance, the power delivered by ALM will be wasted by its protection circuit.
It would be desirable to have a scheme dealing with the power protection and signal delivery problems in card emulation mode or tag (PICC) design for near field communication (NFC) and Radio Frequency Integrated Circuit (RFIC) application.